JPS6120802A - Method and instrument for measuring work - Google Patents

Abstract

PURPOSE:To simplify the entire structure of the instrument, and to maintain excellent measurement precision and secure detection performance with no probability of wrong signal generation by using variation in the pressure of compressed air as an output signal of work measurement. CONSTITUTION:The compressed air with constant pressure is charged in an air chamber 24, and a filler 14 is pressed to before a measuring bar body 12, i.e. toward a work 10 with the internal pressure based upon the compressed air and the spring force of a pressure spring 21 and further held at a constant position while a tapered engaging surface 19 provided to ita base end part is in complete contact with a tapered bearing surface 20 provided to the tip part of the bar body 12. When the work 10 contacts a measuring sphere 11 mounted atop of the filler 14 during the measurement of the size of the work 10, an air flow from the filler support position of the bar body 12 varies in leakage according to the displacement of the filler 14, and a contact signal is outputted when the back pressure drops to a preset ''threshold value''.

Description

[Detailed Description of the Invention] The present invention relates to a method and device for measuring a workpiece.More specifically, the present invention relates to a method and device for measuring a workpiece. The present invention relates to a workpiece measuring method and apparatus that controls the amount of air leaked from the air and outputs a contact signal between the workpiece and a measuring ball by utilizing changes in back pressure caused by the air leakage.

Various automatic measurements are performed using a triaxial contact detector known as a blood touch sensor. As an example of automatic measurement, the procedure for measuring the center position of a hole in a workpiece will be explained below. As shown in FIGS. 4 and 5, the feed shaft of a numerically controlled machine tool, such as a machining center, is driven to move the touch sensor (2) attached to the main shaft in the plus or minus direction of the X-axis. A touch trigger signal is transmitted from the touch sensor at the moment of contact with the workpiece (1), and the amount of movement of the numerically controlled machine tool at this time or the workpiece's
The axial length or width center is determined. By performing the same measurement operation along the X-axis direction, the workpiece (
1) The hole diameter or hole center position can be measured.

Touch sensor + (2) is commercially available with various structures, but the basic measurement principle of the existing touch sensor (2) is that the measuring ball (3) is attached to the tip of the touch sensor.
The mainstream is one that turns on and off electrical continuity by utilizing the displacement that occurs when the metal contacts the workpiece (1).

However, when relying on such a measurement principle, the overall structure of the measurement bar including the touch sensor becomes complicated due to the use of electrical continuity, and furthermore, the overall structure of the measurement bar including the touch sensor becomes complicated. An electrical signal transmission/reception device is required to transmit the electrical detection signal to the spindle head of the numerically controlled machine tool.

On the other hand, the touch sensor (2) is generally attached to a shank portion having the same shape and dimensions as the tool, and is attached to an automatic tool changer (Auto+atic ToolChang).
In order to automatically move between the spindle of a numerically controlled machine tool and the tool magazine using the ATC (abbreviated as ATC), it is necessary to be equipped with a non-contact electrical signal exchange device. Such non-contact electric signal exchange devices are known to use electromagnetic induction or photodiodes, but it is difficult to install these types of electric signal exchange devices at workpiece processing sites. Then, there is a risk that fine powder of the casting, chips of the workpiece, etc. may adhere, and an erroneous signal may be transmitted.

The present invention eliminates the above-mentioned inconveniences that occur when measuring the dimensions of a workpiece using a known non-contact electrical signal exchange device that uses photodiodes or electromagnetic induction. The main object of the present invention is to provide a new method and apparatus for measuring a workpiece that uses changes in the pressure of compressed air as an output signal for measuring the workpiece.

Another main object of the present invention is to provide a three-wheel contact detector that uses a compressed air pressure signal instead of an electrical detection signal, with improved structural simplicity and improved measurement accuracy.

In view of the above-mentioned object to measure the dimensions of the workpiece (10), the present invention provides a method for measuring the size of the measurement bar body (12) from the tweeter support portion (13) in response to the displacement of the measurement ball (11) for measuring the dimensions of the workpiece (10). A workpiece measurement method that changes the amount of airflow leakage, detects a change in back pressure on the tweeter (14) due to the airflow leakage, and outputs a contact signal between the workpiece (10) and the measuring ball (11). This is the first summary.

Furthermore, the present invention provides a measuring bar (16) for measuring a workpiece (10) mounted on the main shaft (15) of a machine tool by an automatic tool changer (ATC), in which air is removed inside the measuring bar body (12). From the introduction port (17) to the tweeter support part (13
), and a tweeter (18) is formed at the tip of the measurement bar body (12).
14) supports the tapered engagement surface (19) provided at the proximal end.

A tapered seat surface (20) is formed, and a tweeter (1) is formed.
4), the tapered engagement surface (19) is pressed against the pressurizing spring (21).
The second gist is a workpiece measuring device in which a three-axis contact detector is formed by disposing the workpiece measuring device so as to be displaceable in the axial direction with respect to the tapered seating surface (20) under a biasing force of be.

A measuring bar (16) with a shank (22) that fits into the main shaft (15) of a large numerically controlled machine tool, such as a machining center (M), has a shape and dimensions that are approximately the same as a general-purpose tool (not shown). ) is automatically called out from a tool magazine (not shown) according to a numerical control program, and can be attached to the main shaft (15) of the machining center (M).

FIG. 1 is a partial longitudinal sectional view of a three-wheeled contact detector constituting the main part of the device of the present invention, in which the main shaft (15) has the measuring bar (16) fitted and fixed in the main shaft head (23). is supported. The measuring bar body (12) connects the shank (22) formed at its base end to the tapered part (15) of the main shaft (15).
24) so that a constant workpiece measurement position can be secured. On the other hand, at the tip of the measuring bar body (12), there is a tweeter (1) that is constantly pressed forward in the axial direction by a pressurizing spring (21) 7.
4) is in a state in which the tapered engagement surface (19) provided at the base end of the tweeter is in close contact with the tapered seat surface (20) formed at the tip of the measurement bar body (12). It is located. A workpiece (10) is attached to the tip of the tweeter (14).
) is used to measure the dimensions of the workpiece (1).
0) so that it can be freely contacted. Measuring bar (16)
The compressed air supplied from a compressed air source (not shown) outside the system is fed into an air chamber (2) formed at the tip of the measuring bar body (12).
An arm (25) for introducing into the measuring bar body (12) is attached in a protruding state from the measuring bar body (12), and a rond (26) is further attached to the measuring bar body (12) from the arm (25). ) and protrudes with the axis direction substantially aligned. Inside the measurement bar body (12), arm (25), and rond (26), there is an air flow path (18) for supplying compressed air introduced from the connection port (27) to the air chamber (24). , (28a) and (28b) are provided in communication. Reference number (29) is a filter disposed within the air flow path to remove dust etc. from the compressed air, and a filter disposed within the air flow path for the purpose of preventing air leakage. A known O-ring is fitted and fixed at a predetermined position. On the other hand, machining center (M)
When the measuring bar (16) is automatically attached to the main shaft (15) by the automatic tool changer (ATC), the measuring bar (23) side receives compressed air supplied from a compressed air source outside the system. 16) A connection device is provided for supplying the inside. That is, the base plate (30) and the camp (31)
A bush (33) that is slidably supported with a slight clearance (32) in the X-Y plane is provided between the bushes, and a spring (33) is installed in the inner diameter hole of the bush. 3
A slider (35) is provided which is pressed by the bushing (3) and is slidable along the axial direction of the bush (33).

When the measuring bar (16) is not attached to the main shaft (15), the slider (35) is attached to the spring (34).
The air passage hole (36) having an open end in the side body of the slider is thus kept closed.

Therefore, when the measurement bar (16) is not attached, the supply of compressed air from the connection port (27) is cut off.

On the other hand, when the measurement bar (16) is attached to the main shaft (15), the tip of the rond (26) comes into contact with the tip of the slider (35), and the slider (35) remains in that state. ) is retracted along the axial direction. As the rear movement of the slider (35) progresses, the air passage hole (36)
transitions from the closed state to the conductive state, and when the measurement bar (16) is completely attached, the compressed air supplied from the connection port (27) is transferred to the measurement bar body (12), the arm (25), and the rond (26). ) in the air flow path (28b), (2
8a) and (18) into the air chamber (24). The reason why the bushing (33) is made to be slidable in the x-y plane is because the measurement bar (16) is attached to the main axis (1).
This is to eliminate the influence of positioning errors of the rond (26) when attaching it to the bushing (33).
), the tips of the rond and bushing are provided with a tapered part for eliminating interference.

The operating principle of the device of the present invention will be explained below. Tweeter (1
In the state shown in FIG. 1, in which the measurement bulb (11) at the tip of 4) is not in contact with the workpiece (10), compressed air with a constant pressure is sealed in the air chamber (24), and the compressed air The tweeter (14) is pressed forward of the measuring bar body (12), that is, toward the workpiece (10), by the internal pressure of the air and the spring pressure of the pressurizing spring (21), and the tweeter (14) is pushed toward the workpiece (10) side. The tapered engagement surface (19) provided at the measuring bar body (12) and the tapered seat surface (20) provided at the tip of the measuring bar body (12) are held in a constant position with almost completely in contact with each other. has been done. The air chamber at this time (24
) leakage of compressed air from the tapered engagement surface (19
) and the tapered seating surface (20), but by improving the taper accuracy, the workpiece (lO) and the measuring ball (11)
The amount of compressed air leaking when there is no contact can be reduced to a negligible extent.

When the measurement ball (11) comes into contact with the workpiece (10), the tweeter (14) is displaced using its proximal end portion having a tapered engagement surface (19) as a fulcrum, and as a result, the tapered engagement surface (19) ) and the tapered seat surface (20), a gap is created,
The amount of compressed air leaking increases in accordance with the displacement of the tweeter (14). The change in the amount of compressed air leakage corresponding to the displacement of the tweeter (14) can similarly occur with respect to any axial displacement of the X-axis, Y-axis, and Z-axis.

On the other hand, the compressed air supply system has a compressed air source (3
7), pressure regulating valve (3B), fixed throttle (39),
It consists of a back pressure detector (40) and a compressed air supply device (41) to the measuring bar (16), and a measuring ball (41).
11) and the workpiece (10), the tweeter (
14), the back pressure detected by the back pressure detector (40) decreases in response to an increase in the amount of leakage. Figure 3 shows the displacement of the tweeter (14) and the back pressure detector (40).
This is a rectangular coordinate diagram showing the relationship between the air pressure and the back pressure detected in the air micrometer, and a characteristic curve similar to that of a known air micrometer is recorded.

When measuring the dimensions of the workpiece (10), the tweeter (14)
When the measuring ball (11) attached to the tip of the measuring bar (11) comes into contact with the workpiece (10), airflow leaks from the tweeter support portion (13) of the measuring bar body (12) in response to the displacement of the tweeter (14). A contact signal is output at point A where the amount changes and the back pressure decreases to a preset threshold value J (Po).

In this way, the dimension or width center of the workpiece (lO) is measured with high precision via a contact signal that converts a change in the amount of leakage of compressed air into a change in back pressure.

In the embodiment illustrated in FIG. 4, a known pressure needle is used as the back pressure detector (40), but in a different embodiment, a pressure converter that converts pressure changes into electrical signals is used. It is also possible to use a back pressure detection device configured to detect the displacement of a device, for example a diaphragm, using a limit switch.

As can be understood from the above explanation, the device of the present invention has an extremely simple overall structure and stable measurement conditions, so it can maintain good measurement accuracy over a long period of time. Can be done. In addition, since contact signals caused by changes in back pressure are used instead of electrical signals, there is a risk of erroneous signals being transmitted even in poor measurement environments where dust or workpiece chips are present. It is possible to ensure good measurement conditions with no detection performance.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view of a three-wheel contact detector according to the present invention, and FIG. 2 is a block diagram of a compressed air supply system formed between a compressed air source and the three-wheel contact detector. Furthermore, Fig. 3 is an orthogonal coordinate diagram showing the relationship between tweeter displacement and back pressure, and Figs. 4 and 5 are explanatory diagrams of the measurement principle of a known three-wheeled contact detector that uses electrical signals. It is. (10) - Workpiece, (11) - Measuring ball, (12
) - Measuring bar body, (13) - Tweeter support part,
(14)...-tweeter, (15)...-main axis, (16)
)...-Measurement bar, (17)--Air inlet, (1
8) - Compressed air flow path, (19) ---- Tapered engagement surface, (20) --- Tapered seating surface, (21) ---
-Pressure spring. 112M

Claims (2)

[Claims] (1) The amount of airflow leaking from the filler support part of the measurement bar body is changed according to the displacement of the measurement ball for measuring the dimensions of the workpiece, and the change in back pressure to the filler due to the airflow leakage is suppressed. A workpiece measurement method characterized by detecting and outputting a contact signal between a workpiece and a measuring ball. (2) In a measurement bar for measuring a workpiece that is attached to the main shaft of a machine tool by an automatic tool changer, a compressed air flow path is formed inside the measurement bar body that extends from the air inlet toward the filler support area. At the same time, a tapered seat surface is formed at the tip of the measuring bar body to support a tapered engagement surface provided at the base end of the feeler, and the tapered engagement surface of the feeler is biased by a pressure spring. A workpiece measuring device characterized in that a three-axis contact detector is disposed below the tapered seating surface so as to be displaceable in the axial direction.